Filter assembly with shaped adsorbent article; and devices and methods of use

ABSTRACT

A filter assembly includes a shaped adsorbent article disposed in a housing. The shaped adsorbent article has one or more projections extending from a surface of the article toward the housing to provide for flow of fluid between the shaped adsorbent article and the housing. The filter assembly may optionally include a diffusion channel for additional filtering and/or one or more porous polymer films disposed over inlet or outlet openings in the housing to reduce or prevent particulate contamination. The filter assembly may be used in a device, such as a computer disk drive, to filter a fluid, such as air, within and/or entering or exiting the device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 09/353,506,filed Jul. 14, 1999, now U.S. Pat. No. 6,168,651 which is acontinuation-in-part of application Ser. No. 09/168,698, filed Oct. 8,1998, now U.S. Pat. No. 6,146,446, which application(s) are incorporatedherein by reference.

FIELD OF THE INVENTION

This invention relates to shaped adsorbent articles, filters utilizingthe articles, and methods and assemblies of use. In particular, theinvention relates to shaped adsorbent articles having projectionsextending from a main body of the article, filters utilizing thearticles, and methods of use.

BACKGROUND OF THE INVENTION

Adsorbent filters have a variety of uses, including uses in electronicequipment and chemical manufacturing and storage. For example, in thecomputer industry, adsorbent filters are used within the housings orcasings of electronic devices to protect the electronic components fromcontaminants, such as water vapor, acid gas, and volatile organiccompounds. For example, disk drives often include adsorbent filterswithin the disk drive and/or provided over an opening in the disk drivehousing to protect the drive components and the disks from contaminants,such as water vapor, hydrocarbons, and/or acid gas. Without suchprotection, these contaminants can lead to stiction, corrosion, and, insome instances, drive failure.

Typically, the adsorbent filter includes an adsorbent material, such asactivated carbon or a desiccant, within the filter. In many conventionalfilters, the adsorbent material is typically provided as loose granularfilter material or as filter material disposed on a polymer carrier. Thepresence of granular adsorbent material can produce particulatecontamination, particularly if a covering around the filter material iscut or torn open. The addition of a polymer carrier reduces the densityof the adsorbent material because of the presence of the carrier and/orair pockets in the adsorbent material. In addition, the polymercarrier/adsorbent material is typically punched or otherwise cut to formthe desired shape, often loosening particles from the carrier which canthen become contaminants. Compression molded adsorbents are described,for example, in U.S. patent application Ser. No. 08/819,851 now U.S.Pat. No. 5,876,487. However, compression molded adsorbents may, at leastin some instances, provide obstruction to fluid flow and therebysubstantially increase the pressure drop over a filter. Thus, there is aneed for new materials and designs of adsorbent filters to increasefilter efficiency and/or to prevent or reduce contamination by theadsorbent material itself.

SUMMARY OF THE INVENTION

Generally, the present invention relates to shaped adsorbent articlesfor use in adsorbent filters. In particular, the present inventionincludes articles, assemblies, and methods of use that have or use ashaped adsorbent article having at least one projection extending from asurface of the article to permit fluid flow, e.g., air flow, between afilter housing and the shaped adsorbent article. In some instances, theshaped adsorbent article is a molded or compression molded adsorbentarticle.

For example, a filter assembly may include a housing and a shapedadsorbent article disposed in the housing. The housing defines aninternal volume and has first and second openings for flow of a fluid,such as air, into and out of the internal volume. The shaped adsorbentarticle has a plurality of projections extending from at least onesurface of the article toward the housing to provide for flow of fluidbetween the shaped adsorbent article and the housing. The filterassembly may be used in a device, such as a computer disk drive, tofilter air within and/or entering or exiting the device.

Another example is an adsorbent filter assembly having a housing, adiffusion channel defined in the housing, and a molded adsorbentarticle. The housing defines an internal volume and includes a firstopening and a second opening with the diffusion channel extending fromthe first opening to the internal volume of the housing. The moldedadsorbent article is disposed within the internal volume of the housingand has at least one surface with a plurality of projections extendingfrom the surface toward the housing to provide for fluid flow betweenthe article and the housing. In some instances, the assembly alsoincludes a porous film disposed over the second opening and/or adhesivedisposed on the housing to adhere the housing to a device, such as acomputer disk drive.

Another example is an adsorbent filter assembly as described above,except the molded adsorbent article has a single projection extendingfrom the surface toward the housing to provide for fluid flow betweenthe article and the housing. The single projection may be centrallypositioned on the surface of the molded adsorbent article, and mayextend or expand over the entire surface. A single such projection maybe disposed on each of two opposite surfaces of the molded adsorbentarticle.

Yet another example is a method of filtering a fluid. A fluid, such asair, flows through an inlet opening in a housing of a filter assembly.The fluid then flows across a shaped adsorbent article disposed withinthe housing. The shaped adsorbent article has at least one projectionextending from at least one surface of the article to direct fluid flowbetween the projections and between the shaped adsorbent article and thehousing. This method can be used to protect a computer disk drive fromcontaminants.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The Figures and the detailed description which follow moreparticularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1A is a schematic top view of one example of a shaped adsorbentarticle according to the invention;

FIG. 1B is a schematic cross-sectional side view of the shaped adsorbentarticle of FIG. 1A;

FIG. 2A is a schematic top view of another example of a shaped adsorbentarticle according to the invention;

FIG. 2B is a schematic cross-sectional side view of the shaped adsorbentarticle of FIG. 2A;

FIG. 3 is a schematic cross-sectional side view of one example of afilter assembly having a shaped adsorbent article according to theinvention;

FIG. 4 is a schematic cross-sectional side view of another example of afilter assembly having a shaped adsorbent article according to theinvention;

FIG. 5A is a schematic top perspective view of one example of a filterhousing for use with a shaped adsorbent article according to theinvention;

FIG. 5B is a schematic bottom perspective view of the filter housing ofFIG. 5A;

FIG. 6A is a schematic top perspective view of one example of a filterhousing for use with a shaped adsorbent article according to theinvention;

FIG. 6B is a schematic bottom perspective view of the filter housing ofFIG. 6A; and

FIG. 7 is a schematic side view of another shaped adsorbent articleaccording to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is believed to be applicable to adsorbent articlesand assemblies and methods of use of adsorbent articles. In particular,the present invention is directed to assemblies, such as adsorbentfilters, that include a shaped adsorbent article to remove contaminantsand to methods of using these assemblies. The terms “adsorb”,“adsorbing”, “adsorbent”, and the like are to be understood to encompassboth adsorption and absorption phenomena and materials. Although otherfluids may be filtered by the filter assembly, the filtration ofcontaminants from air will be used as an illustration. While the presentinvention is not so limited, an appreciation of various aspects of theinvention will be gained through a discussion of the examples providedbelow.

FIGS. 1A and 1B are schematic top and cross-sectional side views,respectively, of one embodiment of a shaped adsorbent article 100 andFIGS. 2A and 2B are schematic top and cross-sectional side views,respectively, of a second embodiment of a shaped adsorbent article 100′.The adsorbent article 100, 100′ includes a main body 110, 110′ with atleast one projection 120, 120′ extending from a surface of the main body110, 110′. Typically, the projections 120, 120′ are formed (e.g., moldedor compression molded) simultaneously with the adsorbent article 100,100′.

The main body 110, 110′ (i.e., the body of the shaped adsorbent articlewithout the projections) can have a variety of shapes. For example, themain body 110, 110′ may be shaped as a disk (e.g., FIGS. 1A and 1B), atablet, a wafer, a cylinder, a parallelepiped (e.g., FIGS. 2A and 2B),or a cube. The size of the shaped adsorbent article 100, 100′ typicallydepends on factors such as the size of the device in which the shapedadsorbent article is to be used, the volume of fluid to be filtered, theexpected lifetime of the filter assembly, and the density of the shapedadsorbent article.

The main body 110, 110′ of the shaped adsorbent article 100, 100′includes at least one projection 120, 120′ extending from at least onesurface of the main body. Typically, the shaped adsorbent article 100,100′ includes at least four and often six or more projections 120, 120′on at least one surface of the main body 110, 110′. In some instances,projections 120, 120′ are provided on two surfaces of the main body, forexample, on two opposing surfaces, as illustrated, for example, in FIGS.1B and 2B. The projections 120, 120′ may be distributed uniformly,according to a pattern, or randomly on a surface of the main body 110,110′. In some instances, all of the projections 120, 120′ are providedaround a peripheral edge of the main body 110, 110′, as illustrated, forexample, in FIG. 2B.

In the embodiment shown in FIG. 7, the main body 110″ of the shapedadsorbent article 100″ includes only one projection 120″ extending fromat least one surface of the main body 110″. In some instances, aprojection 120″ may be provided on each of two surfaces of the mainbody, for example, on two opposing surfaces, as illustrated, forexample, in FIG. 7. The projection 120″ may be sized so as to extendfrom the entire surface of the main body; that is, the projection 120″may occupy the entire surface. In some embodiments, the singleprojection 120″ on each of one or two surfaces gives those surfaces adomed (e.g., hemispherical) shape.

The projections 120, 120′, 120″ can have a variety of shapes. Forexample, the projections can be hemispheres, cylinders, cones, truncatedcones, cubes, parallelepipeds, or other geometrically regular orirregular shapes. All of the projections 120, 120′, 120″ on a shapedadsorbent article 100, 100′, 100″ may have the sane shape or there maybe two or more types of differently shaped projections 120, 120′, 120″on an article 100, 100′, 100″. The cross-sectional dimensions (e.g.,length, width, and/or diameter) of the projections 120, 120′, 120″ maydepend on factors, such as, for example, the size of the shapedadsorbent article, the size of the surface from which the projectionsextend, the number of projections, and the desired amount of filtering.The distance separating the projections may depend on the density of theprojections on the surface, the size of the surface, the size and shapeof the projections, and the arrangement of the projections. If a singleprojection 120″ is present on a surface, the projection 120″ may occupythe entire surface area.

The distance that the projections 120,120′, 120″ extend from the mainbody 110, 110′, 110″ can vary over a wide range. The distance istypically large enough to allow a fluid, such as air, to flow betweenthe projections 120, 120′, 120″, yet still make sufficient contact withthe main body 110, 110′, 110″ and projections 120, 120′, 120″ to producea desired amount of filtering.

The projections 120, 120′, 120″ define, at least in part, a path forflow of air (or another fluid) between a filter assembly housing (notshown) and the main body 110, 110′, 110″ of the shaped adsorbent article100, 100′, 100″. The path defined at least in part by the projections120, 120′, 120″ is typically around and/or between the projections 120,120′, 120″. This configuration allows air to flow more freely throughthe filter assembly as compared to using a shaped adsorbent articlewithout projections.

Air, as well as contaminants carried by air, are in contact with thesurface of the shaped adsorbent article 100, 100′, 100″. This permitsthe shaped adsorbent article 100, 100′, 100″ to filter the air byadsorbing contaminants. It is thought, although not necessary to theinvention, that most of the air does not travel through the shapedadsorbent article, but rather around the article. It is also thoughtthat the contaminants are adsorbed on the surface of the shapedadsorbent article and then diffuse into the interior of the article.

In addition to providing a path for fluid flow around the shapedadsorbent article 100, 100′, 100″ the projections 120, 120′, 120″ mayalso provide an increased surface area for interaction with the fluid.The increase in surface area is typically related to factors, such as,for example, the number of projections, their cross-sectional area, thedistance the projections extend from the main body, and the shape of theprojections. The projections 120, 120′, 120″ may also provide obstaclesto the direct flow of air over the surface of the shaped adsorbentarticle and may redirect air flow (e.g., by producing eddy currents)toward that surface, thereby increasing filter efficiency.

A single projection 120″ on the surface of the shaped adsorbent article100″ increases the surface area available for interaction with the fluidin relation to the surface area available if no projection were present.Likewise, a single projection 120″ on each of two opposite surfaces ofthe shaped adsorbent article 100″ further increase the surface areaavailable.

In another embodiment, a projection, or a plurality of projections, maybe positioned on a first projection on an adsorbent article. Forexample, projections 120, such as illustrated in FIGS. 1A and 1B, may bepositioned on projection 120″ of adsorbent article 100″ shown in FIG. 7.These multiple layers of projections may provide an advantage ofincreased air flow across the shaped adsorbent article.

The shaped adsorbent article 100, 100′, 100″ is typically formed of amaterial that can be easily formed into a shape that the materialretains over time, often, following a curing (e.g., heating) or otherprocess to set the material in the shape. The term “shaped” means thatthe adsorbent article is formed into a shape that the articlesubstantially retains during the normal or expected lifetime of a filterassembly. The shaped adsorbent article may be formed from a free-flowingparticulate material that is shaped into a non-free-flowing article. Theshaped adsorbent article may be formed by a molding, preferably, acompression molding, process. These particular processes can be used toform the shaped adsorbent article in a variety of shapes withreproducible projections.

The shaped adsorbent article is not a conglomerate of granular particlesthat are held together by an outer skin or cover, but is typically astructure that retains its shape without external support. However, itwill be understood that application of force may break or otherwisedislodge portions of the article. The shaped adsorbent article mayprovide advantages over conventional filters including, adsorbentfilters formed by depositing an adsorbent material on a carrier film orgranular adsorbent material provided in a porous container or covering.The shaped adsorbent article can often be formed with a density ofadsorbent material that is significantly greater, often at least 1.5 totwo times greater, than these conventional filters. This is particularlyuseful as devices, such as disk drives, become smaller and the need forfiltration becomes greater. Moreover, the possibility of particulatecontamination by the filter itself may be greater when using theconventional granular or adsorbent/carrier configurations, as opposed tousing a shaped adsorbent article. Furthermore, the addition ofprojections typically permits better flow of air (i.e., a lower pressuredrop) through the filter assembly than would be available using a shapedadsorbent article without projections.

At least a portion of the material used in the shaped adsorbent articlehas adsorbent properties. The shaped adsorbent article is often formedusing an adsorbent material and a binder. The adsorbent material caninclude physisorbents and/or chemisorbents, such as desiccants (i.e.,materials that adsorb or absorb water or water vapor) and/or materialsthat adsorb volatile organic compounds and/or acid gas. Suitableadsorbent materials include, for example, activated carbon, activatedalumina, molecular sieves, silica gel, potassium permanganate, calciumcarbonate, potassium carbonate, sodium carbonate, calcium sulfate, ormixtures thereof. The adsorbent material may adsorb one or more types ofcontaminants, including, for example, water, water vapor, acid gas, andvolatile organic compounds. Although the adsorbent material may be asingle material, mixtures of materials are also useful.

For typical operation, an adsorbent material that is stable and adsorbswithin a temperature range of −40° C. to 100° C. is preferred.Preferably, the adsorbent material is a powder (passes through 100 meshU.S.S.) or granular material (28 to 200 mesh) prior to forming theshaped adsorbent article.

The binder is typically dry, powdered, and/or granular and can be mixedwith the adsorbent. In some embodiments, the binder and adsorbentmaterial are mixed using a temporary liquid binder and then dried.Typically, a binder is used that does not completely coat the adsorbentmaterial. Suitable binders include, for example, microcrystallinecellulose, polyvinyl alcohol, starch, carboxyl methyl cellulose,polyvinylpyrrolidone, dicalcium phosphate dihydrate, and sodiumsilicate.

Preferably the composition of the shaped adsorbent article includes atleast about 70%, by weight, and typically not more than about 98%, byweight, adsorbent. In some instances, the shaped adsorbent articleincludes 85 to 95%, preferably, approximately 90%, by weight, adsorbent.The shaped adsorbent article typically includes not less than about 2%,by weight, binder and not more than about 30%, by weight, binder. Insome instances, the shaped adsorbent article includes about 5 to 15%,and, preferably, about 10%, by weight, binder.

In some instances, it may be desirable to include a small amount oflubricant such as PTFE (Teflon® powder) within the composition, in orderto facilitate mold release. When such is used, preferably no more thanabout 10%, and more preferably less than about 3% of the composition,comprises added lubricant. If a lubricant is used, preferably a minimumamount effective to accomplish a desirably reproducible mold release, isused.

The shaped adsorbent article can be formed using a variety ofcompression molding or tablet-forming techniques. Generally all that isrequired is sufficient pressure and/or heat to ensure brick integrityunder ordinary handling and manufacturing conditions. A compression suchthat a given volume contains about 0.8 to 1.75 times (preferably 1 to1.75 times, most preferably greater than 1 time), by weight, adsorbentby comparison to the amount of adsorbent that would occupy the samevolume if it were left in a granular, free-flowing state, is generallyadequate and desirable. To accomplish this, such techniques asconventional tabletting are readily adaptable. Generally tablettingpressures on the order of 12,700 to 25,500 psi will suffice. It may bepossible to use lower pressures by optimizing the formulation, ormodifying the binder, for any selected application and geometry. Inaddition to pressure, heat may be used to set the binder. The amount ofheat may depend on the binder and/or adsorbent material.

Preferably, for typical uses in electronic components, an overall bulkvolume for the compression molded item within the range of about 0.008to 262 cm³ will be preferred, more typically 0.26 to 18 cm³. In thiscontext, the term “bulk volume” is meant to refer to the volumecalculated from either the compression mold cell or the outsidedimensions to the resulting compression molded product.

FIG. 3 illustrates one example of the disposition of a shaped adsorbentarticle 300 in a filter assembly 350. Although only one shaped adsorbentarticle is illustrated, it will be understood that, in some instances,more than one shaped adsorbent article (e.g., one shaped adsorbentarticle containing activated carbon and another article containing adesiccant) may be used. The filter assembly 350 includes a housing 360with an inlet opening 370 and an outlet opening 375. As illustrated, theprojections 320 on the surface of the shaped adsorbent article 300extend outward from a surface of the main body 310 of the article 300toward the housing 360. Although this example is described with respectto air flowing through the inlet opening 370 into an internal volume ofthe housing 360 and then through the outlet opening 375, it will beunderstood that air may also flow in the opposite direction.

The housing 360 may be, for example, an outer covering, a casing, or ashell. The housing 360 is typically formed from a plastic material, suchas, for example, polycarbonate, polyvinyl chloride, nylon, polyethylene,polypropylene, or polyethylene terephthalate (PETG). The housing 360 maybe a single piece or, alternatively, the housing may be formed as two ormore pieces that are combined together using, for example, an adhesive,mechanical connectors, heat sealing, and/or ultrasonic welding to form,for example, a perimeter seal. In other embodiments, the housing 360 maybe a porous polymer film or pouch around the shaped adsorbent articleand formed from, for example, polyethylene, polypropylene,polytetrafluoroethylene, or expanded polytetrafluoroethylene. In theseembodiments, an inlet opening and/or outlet opening may be unnecessaryas the film or pouch is porous.

Optionally, a porous filter layer (not shown) may be provided over theinlet opening and/or outlet opening. The porous filter layer may includea porous polymer film, such as, for example, a porous polyethylene,polypropylene, polytetrafluoroethylene, or expandedpolytetrafluoroethylene film. The porous filter layer may also include awoven or nonwoven scrim or support layer to support the porous polymerfilm. This porous filter layer may be particularly useful to preventparticulate matter from entering and/or exiting the inner volume of thehousing.

A surface of the housing may be coated with an adhesive (not shown) toattach the filter assembly to a wall of a device, such as, for example,a computer disk drive. In particular, the adhesive may be coated orapplied on the surface of the housing having the inlet opening or outletopening so that the filter assembly can be placed over an inlet oroutlet port in a housing of the device. In addition, an interior surfaceof the housing may be coated with adhesive to adhere the shapedadsorbent article to the housing. The adhesive on an exterior and/orinterior surface of the housing may be, for example, a single layer ofan adhesive material or a carrier film with adhesive on two opposingsides (e.g., a double-sided adhesive tape).

FIG. 4 illustrates another example of a filter assembly 450. The filterassembly 450 includes a shaped adsorbent article 400 with projections420 extending from at least one surface of the article 400. The shapedadsorbent article 400 is disposed within a housing 460 that has an inletopening 470 and an outlet opening 475. A filter layer 455 is disposedover the outlet opening 475. The inlet opening 470 is formed using anoptional extension 472 from the housing 460 that can be positionedwithin a port, such as an inlet or outlet port, in a device housing tofilter air entering or exiting the housing. In addition, an adhesivelayer 485 is provided on the surface of the housing containing the inletopening 470. An optional release liner 495 may be provided over theadhesive layer 485 and removed when the filter assembly is to beattached at a desired location in the device (e.g., computer disk drive)housing.

The housing 460 is typically formed to hold an appropriately sized andshaped adsorbent article. FIGS. 5A and 5B illustrate one embodiment of ahousing 460′ for use with, for example, a disk-shaped adsorbent article,such as the article 100 illustrated in FIGS. 1A and 1B. FIGS. 6A and 6Billustrate another embodiment of a housing 460″ for use with, forexample, a parallelepiped-shaped adsorbent article, such as the article100′ illustrated in FIGS. 2A and 2B.

The housing 460 is usually formed from a plastic material, such as, forexample, polycarbonate, polyvinyl chloride, nylon, polyvinylpyrrolidone, polyethylene, polypropylene, or polyethylene terephthalate(PETG), although, in some embodiments, porous polymer films or pouchesmay also be used. The housing 460 is typically formed by molding thehousing material into a desired shape, although other methods of formingthe housing 460 may also be used. The housing 460 may be a single piece,as illustrated in FIGS. 4, 5A, 5B, 6A, and 6B, or, alternatively, thehousing may be formed as two or more pieces that are combined togetherusing, for example, an adhesive, mechanical connectors, heat sealing,and/or ultrasonic welding to form, for example, a perimeter seal.

The housing may optionally include one or more ribbed members 445′, 475″along at least one sidewall of the housing, as illustrated in FIGS. 5Band 6A. These ribbed members may be provided to separate the shapedadsorbent article from contact with the sidewall of the housing,particularly for those surfaces of the shaped adsorbent article that arenot provided with projections.

An optional diffusion channel 435 may also be formed in the housing 460,as illustrated in FIGS. 4, 5A and 5B (diffusion channel 435′), and 6Aand 6B (diffusion channel 435″). The diffusion channel 435 may extendfrom the inlet opening 470 at the exterior of the housing 460 to anaperture 474 opening on the inner volume of the housing 460. Thediffusion channel 435 can have a variety of shapes, as illustrated, forexample, in FIGS. 5A and 6B. The channel 435 may be formed with thehousing (e.g., molded or compression molded) or may be later formed inthe housing by cutting or otherwise removing material from the housing.Alternatively, a separate diffusion channel layer, with a diffusionchannel defined therein, may be formed as a separate piece and insertedinto the interior of the housing or attached, for example, adhesively,to the exterior of the housing. This separate piece may be, for example,a molded article or a polymer film having a channel formed therein.

The filter layer 455 typically includes a porous polymer film made from,for example, polyethylene, polypropylene, polytetrafluoroethylene, orexpanded polytetrafluoroethylene. The filter layer 455 may optionallyinclude a woven or nonwoven scrim or support layer to support the porouspolymer film. The outlet opening 475 may range from a relatively smallhole in the housing 460 (see, for example, FIG. 3) to include an entireside of the housing 460, as illustrated in FIG. 4. The filter layer 455typically covers the entire outlet opening 475, but may also extendbeyond the outlet opening 475. The filter layer 455 may, for example,prevent particulate material from entering or exiting the interior ofthe filter assembly 450. Particulate material external to the filterassembly can block pores on the shaped adsorbent article 400, renderingthe article less effective. In addition, particulate material from thefilter assembly, for example, particulate material shed or broken offthe shaped adsorbent article, can further contaminate the device. Thefilter layer 455 may prevent or reduce these occurrences. The filterlayer 455 may optionally remove some contaminants from the fluid.

The adhesive layer 485 may be, for example, a coating of an adhesivematerial on the housing 460 or a double-sided adhesive tape (e.g., anadhesive carrier, such as a polymer film, with adhesive coated on twoopposing surfaces). An opening may be formed in the adhesive layer 485,particularly if the adhesive layer is a double-sided adhesive tape, topermit fluid flow into the inlet opening 470 and/or to fit around theextension 472. The release liner 495 is typically a film, for example, apolymer film, that can be removed from the adhesive layer 485 leavingmost, and, preferably, all, of the adhesive layer 485 disposed on thehousing 460. The release liner 495 may extend beyond the adhesive layer485 to allow for easy removal.

Air can flow through the inlet port of the device, into the extension472 and inlet opening 470, along the diffusion channel 435, and throughthe aperture 474 to the internal volume of the filter housing 460. Theair then flows over the surface of the shaped adsorbent article 400 andbetween the projections 420, so that contaminants in the air can beadsorbed by the shaped adsorbent article 400. The air then flows throughthe outlet opening 475 and the filter layer 455 into the device. Inaddition or alternatively, air within the device can flow through thefilter layer 455 and outlet opening 475 and into contact with the shapedadsorbent article 400 to remove contaminants formed within the device.

In an alternative embodiment, an internal surface of the housing mayinclude stand-off projections that separate the shaped adsorbent articlefrom the non-projecting portion of the internal surface. These stand-offprojections may be provided on the side, top, or bottom internalsurfaces. The shaped adsorbent article may or may not have projectionsextending from the side that is facing the internal surface withstand-off projections. As an example, the device of FIG. 4 could bemodified to have stand-off projections extending from the top internalsurface of the housing (i.e., the internal surface from which air exitsfrom the diffusion channel or inlet opening) and the shaped adsorbentarticle modified to have no projections extending towards the topinternal surface with stand-off projections.

Accordingly, a filter assembly can be formed using a shaped adsorbentarticle with at least one projection extending from the article toprovide for flow of a fluid between a main body of the adsorbent articleand a housing. This configuration can provide for filtering of the fluidusing denser filter material (to reduce volume of the filter, forexample) and/or less pressure drop.

EXAMPLES OF SHAPED ADSORBENT ARTICLES

One suitable example of a shaped adsorbent article is a disk, such asthe embodiment illustrated in FIGS. 1A and 1B, having a main body with adiameter of at least 2 mm and not more than 20 mm. The diameter of thisshaped adsorbent article is typically 3 to 12 mm. This shaped adsorbentarticle has a thickness of at least 0.5 mm and not more than 8 mm. Thethickness is typically 0.7 to 5 mm.

Another example of an adsorbent article is a parallelepiped, such as theembodiment illustrated in FIGS. 2A and 2B, having a main body withlength and width dimensions (that are not necessarily the same) of atleast 3 mm and not more than 30 mm. The length and width dimensions aretypically 8 to 20 mm. The thickness of this shaped adsorbent article isnot less than 1 mm and not more than 20 mm. The thickness is typically 4to 15 mm.

Yet another example of an adsorbent article is a domed article, such asthe embodiment illustrated in FIG. 7. A single protrusion 120″ ispositioned on each of opposite sides of main body 110″ to provide anadsorbent article 100″ having a domed shape. If the overall shape of theadsorbent article is circular, i.e., a disk, then adsorbent article 100″may resemble a circular pill. Alternately, the overall shape of theadsorbent article may be a shape other than circular, and may be, forexample, rectangular. A domed rectangular adsorbent article 100″ mayresemble a caplet.

No matter what the overall shape is of the shaped adsorbent article, theshaped adsorbent article 100″ typically has an overall thickness of atleast 0.5 mm and typically not more than 8 mm. The thickness “H” of themain body 110″, as illustrated in FIG. 7, is generally at least 0.35 mmthick and typically not more than about 4 mm. A suitable range for thethickness H of main body 110″ is about 1 mm to about 4 mm. The height orthickness “h” of the protrusion 120″, as illustrated in FIG. 7, isgenerally at least 0.1 mm and typically not more than 3 mm. A suitablerange for the height h of the protrusion 120″ is generally about 0.5 mmto 2 mm.

When multiple projections are used, the projections have a dimension(i.e., length, width, and/or diameter) that is at least 0.2 mm and notmore than 5 mm. The length, width, and/or diameter of the projections istypically 0.3 to 2 mm, although the protrusion may cover the entiresurface of the main body of the shaped adsorbent article. If multipleprojections are positioned on a surface, the nearest distance betweenany two projections on the same surface is at least 0.2 mm and not morethan 5 mm. The nearest distance is typically 0.5 to 3 mm. Theprojections extend at least 0.05 mm and not more than 1 mm from thesurface of the shaped adsorbent article. The projections typicallyextend 0.1 to 0.5 mm. If multiple projections are positioned on asurface, usually at least about 2% and not more than about 50% of thesurface area of a particular surface of the shaped adsorbent article isoccupied by the projections. Typically, the projections cover about 5 to25%, and, preferably, about 7 to 20% of a particular surface. If asingle projection is on a surface, such as illustrated in FIG. 7, thisone projection may cover about 10 to 100% of the surface, and typicallycovers about 50 to 100% of the surface. The projections increase thesurface area of the shaped adsorbent article that is exposed to thefluid by at least about 1%. Typically, the surface area of a surface isincreased by about 1 to 25% or more, preferably by 5 to 20%.

One example of a suitable shaped adsorbent article is made fromadsorbent material that includes at least 70%, by weight, activatedcarbon to filter volatile organic compounds. Preferably, this shapedadsorbent article includes 85 to 100%, by weight, activated carbon. Thisshaped adsorbent article can include up to 30%, by weight, desiccant oracid gas adsorbent, such as, for example, potassium carbonate or calciumcarbonate. Preferably, the shaped adsorbent article includes 1 to 15%,by weight, desiccant or acid gas adsorbent.

Another example of a suitable shaped adsorbent article has adsorbentmaterial that includes at least 75%, by weight, silica gel and up to25%, by weight, activated carbon. This shaped adsorbent article caninclude 75% to 100%, preferably, 85% to 95%, by weight, silica gel and 0to 25%, preferably, 5 to 15%, by weight, activated carbon. In addition,the shaped adsorbent article may include up to 10%, preferably, 1 to 7%,by weight, desiccant or acid gas adsorbent.

In Table I, some usable materials for the shaped adsorbent article areidentified.

TABLE I USABLE MATERIALS FOR SHAPED ADSORBENT ARTICLE Component FunctionSupplier(s) and Sample Products Silica Gel Water Vapor Adsorption GraceDavison (Grade 11 or Syloid 63) Baltimore, MD 21203-2117; Fuji Sylisia(Type A or Type B) Portland, OR 97204 Activated Carbon Adsorption oforganic vapors, Barnebey and Sutcliffe (209C; 209C hydrocarbons and/oracid gases KINA) Columbus, OH 43216 Potassium Carbonate Adsorption ofacid gases Aldrich, Milwaukee, WI Sodium Carbonate Adsorption of acidgases Aldrich, Milwaukee, WI Microcrystalline Binder FMC (Lattice NT-050or NT-006) Cellulose Philadelphia, PA 19103 Teflon Powder LubricantDuPont (Zonyl MP 1100) Wilmington, DE 19805 Polyvinyl Alcohol Binder AirProducts (Airvol 203S) Allentown, PA Starch Binder ADM (Clineo 718)Clinton, IA Carboxyl Methyl Binder Hercules (Aqualon 7MX) CelluloseWilmington, DE 19894 Polyvinyl pyrrolidone Binder GAF ChemicalsCorporation (Plasdone) Wayne, NJ 07470 Sodium Silicate Binder Aldrich,Milwaukee, WI Dicalcium Phosphate Dihydrate Binder Rhone Poulenc(DI-TRB) Shelton, CT

The shaped adsorbent article can be formed by combining the adsorbentmaterial with a binder. Typically, the shaped adsorbent article includes70 to 98%, by weight, adsorbent material and 2 to 30%, by weight,binder. One suitable shaped adsorbent article includes about 87%, byweight, activated carbon, about 3%, by weight, potassium carbonate, andabout 10%, by weight, polyvinyl pyrrolidone. The adsorbent material andbinder can be compression molded using heat and pressures on the orderof 12,700 to 25,500 psi to form the shaped adsorbent article withprojections. Additional description of materials for the shapedadsorbent article and methods for forming the shaped adsorbent articleare described in U.S. Pat. No. 5,876,487, incorporated herein byreference.

In some embodiments, the density of material (e.g., carbon) in theshaped adsorbent article is in the range of 0.35 to 0.7 g/cm³. Thedensity of material in the internal volume of the housing could be inthe range of 0.2 to 0.7 g/cm³. In some instances, the pressure dropthrough the filter may be in the range of 0.25 to 5 cm of water measuredat a 30 cm³/min flow rate.

The present invention should not be considered limited to the particularexamples described above, but rather should be understood to cover allaspects of the invention as fairly set out in the attached claims.Various modifications, equivalent processes, as well as numerousstructures to which the present invention may be applicable will bereadily apparent to those of skill in the art to which the presentinvention is directed upon review of the instant specification.

We claim:
 1. A method of protecting a disk drive from contaminants, themethod comprising steps of: positioning, within the disk drive, a filterassembly comprising a non-porous plastic filter housing defining aninternal volume and having a first opening and a second opening for flowof air into and out of the internal volume, and a compression moldedadsorbent article disposed in the filter housing; flowing air through anfirst opening in the housing of the filter assembly; and flowing the airacross the shaped adsorbent article and between the shaped adsorbentarticle and the housing, wherein the filter assembly further comprises adiffusion channel between the first opening and the internal volume andthe method further comprises flowing air through the diffusion channeland into the internal volume of the filter assembly.
 2. The method ofclaim 1, wherein the diffusion channel extends between the first openingon an exterior of the housing to an aperture that opens into theinterior volume of the filter housing, wherein the first opening andaperture do not overlap.
 3. The method of claim 1, wherein the diffusionchannel forms a curved path from the first opening to the internalvolume of the filter housing.
 4. A method of protecting a disk drivefrom contaminants, the method comprising steps of: positioning, withinthe disk drive, a filter assembly comprising a non-porous plastic filterhousing defining an internal volume and having a first opening and asecond opening for flow of air into and out of the internal volume, anda compression molded adsorbent article disposed in the filter housing;flowing air through an first opening in the housing of the filterassembly; and flowing the air across the shaped adsorbent article andbetween the shaped adsorbent article and the housing, wherein thehousing further comprises at least one ribbed member extending from asidewall of the housing and into the internal volume of the housing toseparate the shaped adsorbent article from contact with the sidewall ofthe housing.
 5. An assembly comprising: (a) a device housing includingtherein a disk drive to be protected; (b) a filter disposed in thedevice housing and comprising: (i) a non-porous plastic filter housingdefining an internal volume and having a first opening and a secondopening for flow of air into and out of the internal volume, and (ii) acompression molded adsorbent article disposed in the filter housing; and(c) a diffusion channel defined within the filter housing and configuredand arranged for air flow from the first opening, through the diffusionchannel, and into the internal volume of the filter housing, wherein thehousing further comprises at least one ribbed member extending from asidewall of the housing and into the internal volume of the housing toseparate the shaped adsorbent article from contact with the sidewall ofthe housing.
 6. An assembly comprising: (a) a device housing includingtherein a disk drive to be protected; (b) a filter disposed in thedevice housing and comprising: (i) a non-porous plastic filter housingdefining an internal volume and having a first opening and a secondopening for flow of air into and out of the internal volume, and (ii) acompression molded adsorbent article disposed in the filter housing; and(c) a diffusion channel defined within the filter housing and configuredand arranged for air flow from the first opening, through the diffusionchannel, and into the internal volume of the filter housing.
 7. Theassembly of claim 6, wherein the diffusion channel extends between thefirst opening on an exterior of the housing to an aperture that opensinto the interior volume of the filter housing, wherein the firstopening and aperture do not overlap.
 8. The assembly of claim 6, whereinthe diffusion channel forms a curved path from the first opening to theinternal volume of the filter housing.
 9. The assembly of claim 6,wherein the diffusion channel is molded into the housing.
 10. Anadsorbent filter assembly, comprising: (a) a non-porous plastic housinghaving a first opening and a second opening and defining an internalvolume; (b) a diffusion channel defined within the housing and extendingfrom the first opening to an aperture that opens into the internalvolume of the housing, wherein the first opening and the aperture do notoverlap; and (c) a compression molded adsorbent article disposed withinthe internal volume of the housing.
 11. The adsorbent filter assembly ofclaim 10, wherein the diffusion channel forms a curved path from thefirst opening to the internal volume of the filter housing.
 12. Theadsorbent filter assembly of claim 10, wherein the diffusion channel ismolded into the housing.
 13. The adsorbent filter assembly of claim 10,wherein the housing further comprises at least one ribbed memberextending from a sidewall of the housing and into the internal volume ofthe housing to separate the shaped adsorbent article from contact withthe sidewall of the housing.